In current mobile Internet architecture, internet protocol version 6 (IPv6) has advantages such as a large address space, a small routing table and high security, and therefore will gradually replace the current protocol, namely internet protocol version 4 (IPv4). However, in the current mobile Internet, there are still a great number of user equipments (UE) with IPv4 addresses and servers with IPv4 addresses. At an early stage of evolution to IPv6, there will be scenarios where a great number of dual-stack terminals (with both IPv4 and IPv6 addresses) access IPv4 network servers (providing IPv4 protocol stack services only). In such scenarios, an IPv6 and IPv4 network address translation (NAT64) technology is generally used in combination with an IPv6 and IPv4 domain name system (DNS64) to implement interworking between an IPv6 network and an IPv4 network. The DNS64 is used to synthesize an A record (IPv4 address) in a domain name system (DNS) query request to an AAAA record (IPv6 address) and then return the synthesized AAAA record to a terminal supporting the IPv6 protocol stack.
In the prior art, only one DNS server or DNS64 server is configured under one access point of a gateway. When a terminal accesses a network through an access point, one access point allocates only a fixed type of addresses to the terminal. For example, when a dual-stack terminal accesses an IPv4 network server, the process is as follows: a DNS address directing to a DNS64 server is allocated to the dual-stack terminal; an A record and an AAAA record query request is sent to obtain an A record (an IPv4 address) and an AAAA record (an IPv6 address synthesized according to the IPv4 address) of the IPv4 network server; preferably, the AAAA record is selected as a destination address and an IPv6 address of the dual-stack terminal is used as a source address to initiate an IPv6-based service request; and, according to an IPv6 and IPv4 interworking policy, the IPv6 request message is translated into an IPv4 request message by an NAT64 and then sent to the IPv4 network server. A response message path of the IPv4 network server is reverse to the request message path, where a response IPv4 message is first sent to the NAT64 and then, after being translated reversely into an IPv6 message by the NAT64, sent to the dual-stack terminal. In this way, the access is completed.
This adds to service loads of the NAT64 and increases expansion costs of an operator, and user experience will be affected due to reasons such as an increased access delay and lower access reliability. In addition, inherent defects of NAT64 are inevitable. For example, an application layer gateway (ALG) is defective, which currently supports only a few network protocols and cannot parse encrypted application layer data.